• Name: Esko Nuutila
  Location: FI - Republic of Finland (Finland)
  
  
• Name: Jari Arkko
  Location: SE - Kingdom of Sweden (Sweden)
  
  
• Name: Ora Lassila
  Location: US - United States of America (United States)

To build:

    make all

To use:

    ./jar.2
    [enter some lisp]

    ./jar.2 < some_lisp_file

NOTE: this entry will likely segfault on invalid input.

Try:

    ./try.sh

    ./try.sh chocolate_cake.lisp

    ./try.sh try.lisp

Judges’ remarks:

This is the most useful program submitted this year. It is a rather large subset of lisp. It has no error recovery, and performs rather poorly in a number of cases. Even so, placing all this functionality in such a small, densely packed program, is impressive enough to win the Best of Show award.

Author’s remarks:

This program implements a Lisp interpreter in 1465 bytes of source. Some sophisticated features supported, e.g. functionals and recursion. The special-forms/functions/variables implemented are:

• +
• -
• *
• <
• ()
• car
• cdr
• cons
• defun
• equal
• function
• if
• lambda
• quote
• t

Below are sample lisp expressions you might choose to try as input. The program implements a conventional lisp listener, i.e. you type in lisp expressions (followed by CR), the program evaluates them and prints out the return values. End execution by typing an end-of-file character.

    (+ 2.5 3.1)
    (defun fib (n)
       (if (< n 2)
           1
           (+ (fib (- n 2)) (fib (- n 1)))))
    (fib 10)
    (defun ! (x) (if (equal x 0) 1 (* x (! (- x 1)))))
    (! 7)
    (defun fn1 (fn) (+ (fn 1 2) (fn 3 4)))
    (defun fn2 (a b) (+ a b))
    (fn1 (function +))
    (fn1 (function fn2))
    (fn1 (function (lambda (z1 z2) (+ z1 z2))))
    (quote a)
    (cons (quote (a b)) (quote (c d e)))
    (cons (quote (f)) ())
    (car (quote (a b c)))
    (cdr (cdr (quote (g h i))))

Please do not leave any whitespace before the first parenthesis when you type your input, or any other unnecessary whitespace. Please try to avoid any undefined variables or functions, wrong number of arguments etc. All these errors are likely to dump core (i.e. there are no error checks in the program).

Traditional Lisp implementations use cons cells as the main data structure. Lists are organized of pointer chains of these cells. In this program, an alternate representation was chosen: char*'s. All list operations, including the ones in the interpreter, are made using string representations of the lists. These operations must count parentheses and skip whitespace. This leads to extremely poor performance!

Primary files

• jar.2.c - entry source code
• Makefile - entry Makefile
• jar.2.orig.c - original source code
• chocolate_cake.lisp - example LISP source file
• fib.lisp - example LISP source file
• try.lisp - example LISP source file
• try.sh - script to try entry

Secondary files

• 1989_jar.2.tar.bz2 - download entry tarball
• README.md - markdown source for this web page
• .entry.json - entry summary and manifest in JSON
• .gitignore - list of files that should not be committed under git
• .path - directory path from top level directory
• index.html - this web page

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